1. Field of the Invention
The present invention relates generally to routing in integrated circuits, and more particularly, to a method and related integrated circuit that improves noise immunity with respect to specific signals in the integrated circuits.
2. Description of the Prior Art
Place and route is an important stage in the design of integrated circuits, which involves placing a variety of active circuit elements and logic gates on the area of the integrated circuit, and followed by routing that adds wires to connect the placed elements and logic gates. Since routing must obey specific design rules and limitations of the semiconductor process, place and route stage is usually complicated. This stage is mostly completed by virtue of automatic placement and routing (APR) tools.
With advances and developments in semiconductor processes, circuit elements in a single integrated circuit have been greatly increased in quantity and density, which increases the workload of the APR tool. Specifically, in order to guarantee the performance of specific circuit elements, and prevent these specific circuit elements from being interfered with, special routing requirements need to be applied. For example, neighboring area around the specific circuit elements needs to be cleared, or no wires are allowed to pass through the top or the bottom of these specific circuit elements.
Besides, signals generated by specific signal sources, such as clock signals, sometimes need special protections. This is because jitters and noises in the clocks signals may undesirably affect performances of high-speed active circuit elements in the integrated circuit. Furthermore, power integrity of a system power/ground mesh varies with status of a load which the power/ground mesh is connected to. For example, in heavy load condition, a voltage supplied by the system power/ground mesh may be shifted, which affects operations of buffers in the integrated circuit. In view of this, the conventional APR tool may not satisfy all the special routing requirements, leading to failure of automatic routing procedure. Hence, there exists a need for providing a solution that improves the conventional routing method.